WO2015188637A1

WO2015188637A1 - Dual-energy radiation system and method for increasing material identification capability of dual-energy radiation system

Info

Publication number: WO2015188637A1
Application number: PCT/CN2015/073183
Authority: WO
Inventors: 王少锋; 李苏祺; 郑建斌; 张丹; 曹艳锋
Original assignee: 北京君和信达科技有限公司
Priority date: 2014-06-09
Filing date: 2015-02-16
Publication date: 2015-12-17
Also published as: CN105203569B; CN105203569A

Abstract

A method for increasing the material identification capability of a dual-energy radiation system and the dual-energy radiation system. The method comprises: implementing dual-energy scan-detection on a test sample of a first type and of a first thickness, when detected data is inconsistent with the test sample, adjusting the pulse number ratio or pulse dose ratio of the dual-energy radiation system until the detected data is consistent with the test sample, and using this as the working ratio of the dual-energy radiation system when formally scanning. The method allows acquisition of the optimal material identification state of the dual-energy radiation system; with scan-inspection being performed in this state, the material identification capability of the dual-energy system is substantially improved.

Description

Dual-energy radiation system and method for improving material recognition capability of dual-energy radiation system

Technical field

The invention relates to the field of radiation imaging technology, and particularly relates to a dual energy radiation system and a method for improving material recognition capability of a dual energy radiation system.

Background technique

With the development of radiation imaging technology, the use of dual energy technology to check the assembly of goods and vehicles has become more and more extensive. Compared with ordinary single-energy ray technology, dual-energy technology can determine the equivalent atomic number Z of the measured object, which can help identify drugs, explosives, special nuclear materials and so on. Typically, such dual energy ray systems use alternating dual energy X-ray radiation sources with a single pulse dose difference between the two energies. Research and analysis show that when the low energy ray pulse penetrates the measured object with a certain thickness, the relative error of the radiation dose detected by the detector becomes larger. As the thickness of the material increases, the ability of the dual energy system to identify the material significantly deteriorates.

Summary of the invention

In view of this, the present invention provides a dual-energy radiation system and a method for improving the material recognition capability of a dual-energy radiation system, and optimizes the radiation pulse number ratio or pulse dose ratio of the dual-energy radiation source to enable the material identification capability of the dual-energy radiation system. Improved.

The invention provides a method for improving the material recognition capability of a dual energy radiation system, comprising: step 1: determining the type and thickness of the test sample; and step 2: performing dual energy scanning detection on the test sample having the first type and the first thickness, Obtaining a scan test result; Step 3: judging whether the detected data is consistent with the test sample according to the scan test result, if the detected type is different from the first type or the detected thickness is different from the first thickness, the detected data and the test If the sample is inconsistent, perform step 4; if the detected type is the first type and the detected thickness is the first thickness, the detected data is consistent with the test sample, and step 5 is performed; step 4: adjusting the number of pulses of the dual-energy radiation system Ratio or pulse dose ratio, return to step two; Step 5: Determine the current pulse number ratio or pulse dose ratio as the scan operation ratio of the dual energy radiation system.

The present invention also provides a dual energy radiation system based on the above method for improving the material recognition capability of a dual energy radiation system, the dual energy radiation system comprising: a dual energy radiation source, a radiation detector, a dual energy image acquisition device, and a judgment processing module The adjustment processing module, the control module and the storage module; wherein the dual energy radiation source emits a dual energy radiation beam to perform dual energy scanning; the radiation detector receives the dual energy radiation beam, converts the dual energy radiation beam into a digital signal, and transmits to the dual energy An image acquisition device; the dual-energy image acquisition device generates a dual-energy radiation image according to the received digital signal; and the determination processing module determines, according to the scan detection result included in the dual-energy radiation image, whether the detected data is consistent with the test sample, and if the determination result is inconsistent The judgment processing module sends the judgment result to the adjustment processing module; if the judgment result is consistent, the judgment processing module sends the judgment result to the storage module; the adjustment processing module adjusts the pulse number ratio or the pulse dose ratio of the dual energy radiation source, and Send the adjustment result to the control module; the control module pairs The radiation source is controlled to enable the dual energy radiation source to emit a dual energy radiation beam according to the adjustment result of the adjustment processing module; the storage module stores the pulse quantity ratio or the pulse dose ratio of the current dual energy radiation source as the judgment result of the judgment processing module. The proportion of the scan job corresponding to the test sample.

The invention also provides a method for improving the material recognition capability of a dual energy radiation system, comprising: step 1: determining the type and thickness of the test sample; and step 2: performing dual energy scanning detection on the test sample having the first type and the first thickness , the scan detection result is obtained; step 3: judging whether the system criterion reaches a minimum value according to the scan detection result, if the minimum value is not reached, step 4 is performed; if the minimum value is reached, step 5 is performed; step 4: adjusting the double The ratio of the pulse number of the radiation system or the pulse dose ratio is returned to step 2; step 5: determining the current pulse number ratio or the pulse dose ratio as the scanning operation ratio of the dual energy radiation system; wherein, the system criterion is

or

The lower corners 1exp and 2exp respectively represent the scanning detection results corresponding to the high energy pulse radiation and the low energy pulse radiation, ΔT is the measurement deviation for the radiation pulse dose, t is the thickness of the material, and Z _i represents the equivalent atomic number of the i-th material. n is a positive integer in which the equivalent atomic number of the material corresponds to the type of material.

The invention also provides a dual energy radiation system based on the above improved dual energy radiation system The method for identifying the capability, the dual-energy radiation system comprises: a dual-energy radiation source, a radiation detector, a dual-energy image acquisition device, a judgment processing module, an adjustment processing module, a control module and a storage module; wherein the dual-energy radiation source emits a double The radiation beam can perform dual-energy scanning; the radiation detector receives the dual-energy radiation beam, converts the dual-energy radiation beam into a digital signal, and sends it to the dual-energy image acquisition device; the dual-energy image acquisition device generates dual-energy radiation according to the received digital signal. The image processing unit determines whether the system criterion reaches a minimum value according to the scan detection result included in the dual-energy radiation image. If the minimum value is not reached, the determination processing module sends the determination result to the adjustment processing module; The small value, the judgment processing module sends the judgment result to the storage module; the adjustment processing module adjusts the pulse quantity ratio or the pulse dose ratio of the dual energy radiation source, and sends the adjustment result to the control module; the control module performs the dual energy radiation source Control, so that the dual energy radiation source emits dual energy radiation according to the adjustment result of the adjustment processing module Beam; and a storage module according to the determination result of the determination processing module, the number of current pulses dual energy radiation source or a pulsed dose ratio than the scan job is stored as a ratio of the corresponding test sample.

DRAWINGS

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a flow diagram of sample based adjustment prior to scanning operation, in accordance with one embodiment of the present invention.

2 is a flow chart based on sample conditioning prior to scanning operation, in accordance with another embodiment of the present invention.

3 is a block diagram showing the structure of a dual energy radiation imaging system according to an embodiment of the present invention.

4 is a flow chart of real-time adjustment during a scan operation in accordance with one embodiment of the present invention.

Figure 5 is a schematic illustration of the state of the dual energy radiation pulse dose ratio of the present invention based on the embodiment of Figure 4.

6 is a block diagram showing the structure of a dual energy radiation imaging system according to another embodiment of the present invention.

Figure 7 is a flow diagram based on sample conditioning prior to scanning operation, in accordance with one embodiment of the present invention.

Figure 8 is a schematic illustration of the state of the dual energy radiation pulse dose ratio of the present invention based on the embodiment of Figure 7.

Figure 9 is a flow diagram of a multi-method adjustment of the number or dose ratio of dual energy radiation pulses in accordance with one embodiment of the present invention.

Figure 10 is a flow diagram of a multi-method adjustment of the number or dose ratio of dual energy radiation pulses in accordance with another embodiment of the present invention.

detailed description

The technical solutions of the present invention are described in detail below in conjunction with the accompanying drawings and specific embodiments.

In the actual scanning process of dual-energy radiation, for a single scanning process, the total dose of the radiation beam emitted by the dual-energy radiation source is a determined value, and the total number of radiation pulses is also a determined value. The present invention treats the high-energy ray pulse and the low-energy ray pulse separately. It is composed of several sub-ray pulses, and the pulse number ratio refers to the ratio of the number of high-energy ray pulses and low-energy ray pulses, and the pulse-to-dose ratio refers to the ratio of the doses of the high-energy ray pulse and the low-energy ray pulse. For dual energy radiation systems, the pulse ratio or dose ratio of the system can be adjusted by adjusting the time between the two energy rays.

1 is a flow chart showing a method for improving the material identification capability of a dual energy radiation system of the present invention, including:

S101: determining a type and a thickness of the test sample;

S102: performing dual-energy scanning detection on the test sample having the first type and the first thickness, and obtaining a scanning detection result;

S103: determining whether the detected data is consistent with the test sample according to the scan detection result, if the detected type is different from the first type or the detected thickness is different from the first thickness, the detected data is inconsistent with the test sample, and executing S104; If the detected type is the first type and the detected thickness is the first thickness, the detected data is consistent with the test sample, and S105 is performed;

S104: adjusting the pulse quantity ratio or pulse dose ratio of the dual energy radiation source, returning to S102;

S105: Determine a current pulse number ratio or a pulse dose ratio as a scan operation ratio of the dual energy radiation source.

In practical application scenarios, if you are interested in a particular material and want to improve the ability of the dual-energy system to identify the material, you can use the above method to scan the test sample of the material, and compare the pulse number ratio or pulse of the dual-energy system. The dose ratio is adjusted to the ideal value, that is, the test result is consistent with the sample itself, and the subsequent object is scanned in the ideal state to obtain an ideal image effect for the material of interest, thereby enabling the dual energy system. The material identification ability has been improved.

For example, a double-energy scan is performed on the test sample with iron having a thickness of t ₁ . If the thickness obtained by the scan is not t ₁ , or the material displayed by the scan is not iron, the image is usually unclear on the dual-energy image. There are many pixel impurities, indicating that the current system has low recognition ability for the sample. In order to improve the recognition ability of the system for the iron material with thickness t ₁ , adjust the time of the two energy radiation beams of the dual energy radiation source, change the pulse number ratio or the dose ratio of the system, re-scan the sample, and observe the scanning image effect. , to determine whether the thickness of the scan is t ₁ , whether the material is iron, if there is a non-conformity, continue to adjust until the thickness of the scan is t ₁ , the material is iron. At this time, the scan results of the dual-energy system are consistent with the properties of the sample itself, indicating that the dual-energy system has the best recognition ability for the iron material having the thickness t ₁ , and the present invention refers to the state of the dual-energy system as the “best material”. Identify status."

With the above embodiment, the conditioned dual energy system the ability to identify a thickness t ₁ good enough iron, formal during a scan job, material identification system in the best condition to be detected if the thickness t of iron ₁ The system can be well identified to avoid misdetection and missed detection.

In the above, according to the scanning result of the dual energy system, the pulse quantity ratio or the dose ratio of the dual energy radiation source is adjusted to achieve the optimal material identification state, and in addition, the method of the present invention can also use the system criterion to judge the double Whether the system can achieve the best material identification state, and achieve the adjustment of the pulse number ratio or the dose ratio.

Specifically, according to the existing research, the attenuation value of the dual-energy ray-penetrating substance is related to the equivalent atomic number of the substance, and the detected data is compared with the existing data to determine the type of the substance to be tested. The following nonlinear integral equations are described:

Where T(E, t, Z) is the transparency of high and low energy rays, and the physical meaning is the dose of the radiation after the energy of E is a dose of 1 and the equivalent atomic number of the thickness is Z. . Before using the dual-energy system for material identification, the system needs to be calibrated to obtain T(E, t, Z) values of materials of different thickness under two energy pulse conditions. After calibration, different energy and different materials can be formed. For T values of different thicknesses, fitting the thickness t gives the T value of the material at all thicknesses.

After the high-energy and low-energy rays of the dual-energy system penetrate the object, the detector can measure the pulse doses T _1exp and T _{2exp of the} two rays (the angles 1 and 2 represent high and low energy rays), and the two kinds of radiation pulse doses There are measurement deviations: ΔT _1exp = T(E ₁ , t, Z) - T _1exp , ΔT _2exp = T(E ₂ , t, Z) - T _2exp . Algorithmically, the essence of dual-energy material recognition is to find the minimum of the following formula:

Find the t and Z that minimize R, and obtain the thickness and equivalent atomic number of the measured object in the calibrated T value table to realize the material identification of the measured object. It can be seen that when the formula (2) reaches the minimum value, the type and thickness of the object to be tested can be obtained.

As shown in Fig. 2, the present invention uses equation (2) as a system criterion for material identification of a dual energy system, and adjusts the pulse number ratio or pulse dose ratio of the system. In the specific calculation, the system calculates whether the formula (2) reaches the minimum value according to the dual-energy scan result of the sample to be tested. If the minimum value is not reached, adjust the pulse ratio or the dose ratio until the formula (2) is reached. The minimum value, the corresponding pulse number ratio or dose ratio is the best material identification state of the dual energy system.

Correspondingly, the present invention provides a dual-energy radiation imaging system 100. The block diagram of the structure is as shown in FIG. 3, including: dual-energy radiation source 10, radiation detector 12, dual-energy image acquisition device 14, determination processing module 16, and adjustment processing module 18. , the control module 20 and the storage module 22; wherein

The dual-energy radiation source 10 emits a dual-energy radiation beam to perform dual-energy scanning, wherein the high-energy radiation beam and the low-energy radiation beam alternately exit the beam;

The radiation detector 12 receives the dual energy radiation beam, converts the dual energy radiation beam into a digital signal, and sends it to the dual energy image acquisition device 14;

The dual-energy image acquiring device 14 generates a dual-energy radiation image according to the received digital signal. When the dual-energy radiation beam passes through the object, the dose of the radiation changes accordingly, and the dual-energy image acquiring device 14 generates a double according to the change. Can image, and can obtain the thickness of the detected object, the equivalent atomic number and other information, if the image is clear enough to indicate that the recognition effect is good;

The determination processing module 16 determines whether the detected data is consistent with the test sample according to the scan detection result included in the dual-energy radiation image. If the determination result is inconsistent, the determination processing module 16 sends the determination result to the adjustment processing module 18; if the determination result is consistent , the judgment processing module 16 sends the judgment result to the storage module 22;

The adjustment processing module 18 adjusts the pulse quantity ratio or the pulse dose ratio of the dual energy radiation source 10, and sends the adjustment result to the control module 20;

The control module 20 controls the dual-energy radiation source 10 to cause the dual-energy radiation source 10 to emit a dual-energy radiation beam according to the adjustment result of the adjustment processing module 18;

The storage module 22 stores the pulse number ratio or the pulse dose ratio of the current dual-energy radiation source 10 as the scan job ratio corresponding to the test sample according to the determination result of the determination processing module 16.

Optionally, the determination processing module 16 may be further configured to determine whether the system criterion (ie, formula (2)) reaches a minimum value according to the scan detection result included in the dual-energy radiation image, and if the minimum value is not reached, the determination processing module 16 The determination result is sent to the adjustment processing module 18; if the minimum value is reached, the determination processing module 16 sends the determination result to the storage module 22.

By using the solution of the invention, the above-mentioned debugging process can be performed on test samples of different thicknesses and different material types, and the parameters for storing the best material identification state corresponding to each sample are recorded (ie, the pulse quantity ratio or dose of the debugged dual-energy radiation source) Ratio), in the subsequent screening of a series of detected objects, the system can switch between the corresponding optimal material identification states according to different detected property parameters (thickness and equivalent atomic number) obtained in real time. It can identify a variety of materials and has high recognition ability.

In the specific operation process, according to the following steps, for the n kinds of measured objects (t _i , Z _i ), i=1, . . . , n, determine the pulse number ratio or dose of each system to reach the corresponding optimal recognition state. ratio:

S111: Select n kinds of measured objects (t _i , Z _i ), i=1, . . . , n;

S112: adjusting a current pulse quantity ratio or a dose ratio of the system, and controlling the dual energy radiation source to alternately output high and low energy pulses according to the adjusted ratio;

S113: Observing the dual-energy image to determine whether there is an object to achieve the best material recognition effect, if the result is yes, proceed to step S114; if the result is no, return to S112;

S114: Record the material that currently reaches the best material recognition effect, and the corresponding pulse quantity ratio or dose ratio;

S115: Whether n kinds of measured objects have obtained their corresponding pulse quantity ratio or dose ratio, if yes, the measurement is ended; if not, then returns to S112.

The above-mentioned n kinds of analytes may select a dual-energy material to identify the test materials used for calibration. Using the above test results, the high- and low-energy pulse ratio or dose ratio of the dual-energy radiation source can be adjusted in real time during the scanning process. The operation process is as follows:

S121: acquiring dual-energy image data in real time when the dual-energy imaging system is working;

S122: selecting a corresponding optimal pulse quantity ratio or a pulse dose ratio for the attribute parameter of the current detected object based on the record of the material obtained in the previous stage and the corresponding pulse quantity ratio or the dose ratio;

S123: Control the ratio of the number of radiation pulses to be output or the dose ratio according to the ratio selected by S122.

On the other hand, in radiation imaging system applications, there is often a single scan dose limit. Under this limitation, the present invention proposes to obtain the optimal working ratio of the dual energy system by calculation, and to reasonably distribute the high energy ray and the low energy ray. The number of pulses or dose is the system that quickly reaches the optimal material identification state. The derivation process of the calculation formula of the optimal distribution ratio of the number of pulses and the dose is described below.

Variant of equation (2) is:

Wherein, I ₁ and I ₂ are doses of high and low energy radiation pulses, respectively, when no material is blocked. ΔI ₁ (t, Z) and ΔI ₂ (t, Z) are the standard deviations of the ray pulse dose after the high and low energy ray pulses pass through a material having a thickness t and an equivalent atomic number Z, respectively. Ignoring the difference in detection efficiency between different detectors, the process of ray and matter follows the binomial distribution:

Where μ ₁ (t,z) and μ ₂ (t,z) are thicknesses t, and the material having the equivalent atomic number Z corresponds to the attenuation coefficient of the two energy pulses. Substituting equation (4) into equation (3) yields:

For a single scan detection process, the total dose of the radiation beam emitted by the dual-energy radiation source is a determined value, and the total radiation pulse number is also a determined value, and the high-energy or low-energy radiation pulse is regarded as composed of several sub-ray pulses, assuming a scanning detection process The total number of pulses of the two energy rays is 2N, wherein the number of pulses of the high energy ray is Nk, the dose is I ₁ , the number of pulses of the low energy ray is N+k, and the dose is I ₂ (that is, the pulse of high and low energy rays) The quantity ratio is Nk:N+k, and the dose ratio is I ₁ :I ₂ ), based on formula (5):

The minimum value of R is required to be R'(k)=0, and the derivative of equation (6) is obtained:

Substituting the parameters t, Z, μ ₁ (t, z), μ ₂ (t, z) of the I ₁ , I _{2 of the} dual energy source and the material of interest (eg a certain thickness of iron) into the formula (7), A value of Nk:N+k can be obtained, which is the optimal distribution ratio of the number of pulses of the two energy rays of the dual energy source. According to the ratio, the alternating dual-energy radiation source output radiation pulse is controlled, and the system is in the best material identification state, and the recognition capability of the thickness of the iron material is the best.

Further, when k=0 in the equation (7), that is, the number of pulses is N-k:N+k=1, there are:

From equation (8), the optimal distribution ratio I ₁ : I ₂ of the pulse doses of the two energy rays of the dual energy source is obtained. Similar to the formula (7), the dual-energy system operating in the optimal dose ratio state has the best ability to recognize the thickness of the iron material, and the dual-energy radiation image has the best effect.

It can be seen that the ray pulse of the radiation source is regarded as a number of sub-ray pulses, and the pulse number ratio problem of different energy rays can be converted into a pulse dose ratio problem, so the conclusion about the pulse number ratio problem is also applicable to the pulse dose ratio problem.

Taking the commonly used 9/6MeV dual energy as an example, Varian's M9A accelerator has a 9MeV ray half-value layer of about 30.5mm iron, a 6MeV ray half-value layer of about 28mm iron, and a mass thickness of 40g/cm. The iron ratio of ² , according to formula (8), the optimum material identification state of the 9/6 MeV radiation dose ratio is about 1.0658:1. When the dose ratio is 1:1, the optimum identification mass for iron is about 22.2 g/cm ² . For the 9/6 MeV dual energy, when the thickness of the iron to be identified is in the range of 1 g/cm ² to 200 g/cm ² , the optimum dose ratio of the 9/6 MeV rays ranges from 0.9208:1 to 1.6756:1.

Taking 3/1.2 MeV dual energy as an example, Varian's M3A accelerator has a 1.2 MeV ray half-value layer of about 16.5 mm and a 3 MeV ray half-value layer of about 23.1 mm. When the thickness of the iron to be identified is in the range of 1 g/cm ² to 70 g/cm ² , the optimum dose ratio of the 3/1.2 MeV rays ranges from 0.7272:1 to 2.7748:1.

In the actual application scenario, different from the foregoing, according to the optimal material identification state of the sample determination system before the start of the formal scan, the system can be adjusted to the most in real time during the formal scan inspection by using formula (7) or (8). Good material identification status, flexible control of the system's ability to recognize different materials. Figure 4 shows the real-time adjustment of the high energy, low energy pulse ratio or dose ratio of the dual energy radiation source during the scanning process.

S201: acquiring dual-energy image data in real time when the dual-energy system is working, and obtaining attribute parameters (thickness of the detected object, equivalent atomic number, and attenuation coefficient) of the current detected object based on the dual-energy image data;

S202: Substituting equation (7) to calculate an optimal pulse ratio, or substituting equation (8) to calculate an optimal dose ratio;

S203: Control the ratio of the number of radiation pulses to be output or the dose ratio according to the ratio calculated by S202. In this way, the dual energy system is quickly adjusted to the optimal material identification state.

FIG. 5 is a schematic diagram of real-time adjustment of a dual-energy radiation pulse dose state in an embodiment of the present invention. When the dual energy system works, the measured object (t ₁ , Z ₁ ) is changed to (t ₂ , Z ₂ ) at a certain time. After the system detects the change of the measured object, the dose of the subsequent radiation pulse is adjusted immediately. In this embodiment, the high energy pulse dose is increased, the low energy pulse dose is correspondingly weakened, and the total dose of the high and low energy pulses is not changed. The advantage of this treatment is that while the system improves material identification, the boundary dose of the system does not change, ie the area of radiation protection does not change.

Accordingly, the present invention also provides a dual-energy radiation system 300, which is shown in FIG. 6, comprising: a dual-energy radiation source 30, a radiation detector 32, a dual-energy image acquisition device 34, an algorithm module 36, and a control module 38; ,

The dual-energy radiation source 30 emits a dual-energy radiation beam, and performs dual-energy scanning on the detected material;

The radiation detector 32 receives the dual energy radiation beam, converts the dual energy radiation beam into a digital signal, and sends it to the dual energy image acquisition device 34;

The dual-energy image acquisition device 34 generates a dual-energy radiation image based on the received digital signal;

The algorithm module 36 is based on the equivalent atomic number and thickness of the detected object according to formula (7) or (8) Calculate the pulse ratio or dose ratio;

The control module 38 controls the dual energy radiation source 30 to emit a dual energy radiation beam in accordance with the pulse dose ratio calculated by the algorithm module 36.

Of course, using the formula (7) or (8), the optimal ratio can be calculated for the sample of interest before the formal scan, and the ratio is used in the formal scan. The specific process is shown in Figure 7:

S301: determining a detection object of interest and related parameters (thickness, equivalent atomic number, and attenuation coefficient);

S302: Calculate an optimal pulse quantity ratio according to formula (7) based on the object parameter, or calculate an optimal pulse dose ratio according to formula (8);

S303: When the dual energy system is in operation, the dual energy radiation source is controlled to alternately output the radiation pulse according to the optimal pulse quantity ratio or the dose ratio calculated in step 302.

8 is a schematic diagram showing the adjustment of the dose state of the dual-energy radiation pulse based on the formula (7) or (8) in the embodiment of the present invention, wherein the horizontal axis is time, the vertical axis is pulse dose, H is a high energy pulse, and L is a low energy pulse. Based on the commonly used 9/6MeV dual-energy linear accelerator, the dose of 9MeV high-energy pulse is about 3 times that of the 6MeV low-energy pulse. Taking the main test object as 100mm thick Fe as an example, the number of pulses available from equation (7) is Nk/N+k=0.6324, that is, the ratio of high and low energy pulses is 0.6324:1, and the dual energy can be alternately issued according to this ratio. The radiation beam, the system recognizes the state of the material as optimal. In practical applications, a ratio closer to 0.6324:1 may also be taken, such as 1:2 or 2:3. Fig. 3(a) shows the conventional alternate dual energy pulse dose, and Fig. 3(b) shows the case where the high and low energy pulse ratio is 2:3. Figure 3(c) shows the case where the high and low energy pulse dose ratio is 1:1. For devices such as X-ray machines and isotope sources, it is also possible to control the dose of the dual energy pulse by controlling the beam exit time, as shown in Figure 3(d). It can be seen that with existing dual energy systems, the ratio of high to low energy pulses is typically 1:1. After the adjustment of the present invention, the ratio of the high and low energy pulses is no longer 1:1, the dose is properly distributed, and the system material identification capability is rapidly and greatly improved.

In practical applications, the embodiment of FIG. 7 can be further optimized. As shown in FIG. 9, after determining the test sample, the optimal pulse number ratio or dose ratio is calculated by using formula (7) or (8), according to the optimal ratio. The sample is scanned, and then the effect of the scanned image is ideal. If the scan result is not ideally different from the sample itself, then the system pulse ratio or dose can be More adjustments are made until the best image quality is obtained; if the scanned image is ideal and can meet the usage requirements, no further adjustment is needed for the optimal ratio calculated using equation (7) or (8).

Further, regarding the system criterion formula (2) used in the present invention, other algorithmic criteria may be used instead. According to the existing research, the algorithm and criterion for dual energy material identification can determine the material type of the detected object by comparing the results of detecting the thickness of the same material by two energy rays. The criterion of the method is:

Where m is the type of material, t is the thickness of the material, Z _i is the equivalent atomic number of the ith material, and Tol _i (Z _i ) is the tolerance set by the material identification algorithm. Based on equation (10), the dual energy identification problem is converted to compare the thicknesses of the i-th material measured by the two energies, if the thicknesses are equal (ie

Or make

Less than the tolerance Tol _i (Z _i ), the equation (10) holds, and the material to be detected is considered to be the i-th material having a thickness t; otherwise, it is compared with the i+1th material.

It can be seen from equation (10) that when the dose of radiation is low or the material is relatively thick, the dose of the radiation reaching the detector after passing through the test material becomes weak, the relative error of the dose measured by the detector increases, and the measured thickness value The larger the error will result in inaccurate material identification. For example, when the high-energy ray pulse passes through the material to be inspected, the relative error of the dose measured by the detector is relatively small. When the low-energy ray pulse passes through the material to be inspected, the relative error of the dose measured by the detector is large, and the latter is the former. Many times, this will result in a large value on the left side of equation (10), which means that material identification is not accurate. Therefore, the ratio of the number of pulses of the two energy ray pulses is appropriately adjusted so that the errors of the two are equivalent, and a better material recognition capability can be obtained.

To this end, after the material calibration of the dual-energy radiation imaging system, the number of pulses of the two energy pulses of the dual-energy radiation source is adjusted for n kinds of measured objects (t _i , Z _i ), i=1, . The ratio or dose ratio is such that the following equation (11) obtains a minimum value, and the corresponding pulse number ratio or dose ratio allows the system to operate in an optimal material identification state:

That is to say, the pulse number ratio or the dose ratio of the dual energy system can also be adjusted by calculating whether or not the equation (11) reaches a minimum value.

Therefore, based on the formula (2) or the formula (11), the pulse quantity ratio or the dose ratio can be adjusted for the dual energy system of the present invention, and the corresponding pulse number ratio or dose when the formula (2) or the formula (11) reaches a minimum value. The ratio is optimal and the system achieves the best material identification status.

In practical applications, the system criterion (2) or the formula (11) can be used instead of the step 404 in the embodiment of FIG. 9 to observe whether the radiation image achieves the best recognition effect, as shown in FIG. 10, using the formula (7). Or (8) after calculating the optimal pulse number ratio or dose ratio, whether the formula (2) or the formula (11) reaches a minimum value, thereby further adjusting the system pulse number ratio or the dose ratio.

By the processing of the embodiment of Fig. 9 or Fig. 10, the error between the theoretical calculation and the actual system difference can be compensated for.

Based on the solution provided by the present invention, in combination with the actual situation, the dual energy system can be adjusted in the range of high and low energy pulse dose ratios ranging from 0.7:1 to 3:1, and a better adjustment effect can be obtained.

For a dual-energy radiation imaging system, embodiments of the present invention can adjust the radiation pulse number ratio or dose ratio of the dual-energy radiation source for different materials, and obtain the optimal material identification state of the system corresponding to different materials, and the system is before the formal scanning. Set to the best material identification status, or switch the working state of the system in real time during work, it can realize dual-energy recognition of a certain material or multiple materials, and the material recognition ability is high. By using the invention to detect material materials of interest, a better dual-energy radiation image can be obtained, and the detection and recognition capability is strong.

The technical solutions of the present invention have been described in detail above with reference to the specific embodiments, which are used to help understand the idea of the present invention. Derivations and variations made by those skilled in the art based on the specific embodiments of the present invention are also within the scope of the present invention.

Claims

A method for improving material recognition capability of a dual energy radiation system, comprising:

Step 1: Determine the type and thickness of the test sample;

Step 2: performing dual-energy scanning detection on the test sample having the first type and the first thickness, and obtaining a scanning detection result;

Step 3: judging whether the detected data is consistent with the test sample according to the scan detection result. If the detected type is different from the first type or the detected thickness is different from the first thickness, the detected data is inconsistent with the test sample, and the steps are performed. 4; if the detected type is the first type and the detected thickness is the first thickness, the detected data is consistent with the test sample, and step 5 is performed;

Step 4: Adjust the pulse quantity ratio or pulse dose ratio of the dual energy radiation system, and return to step 2;

Step 5: Determine the current pulse number ratio or pulse dose ratio as the scan operation ratio of the dual energy radiation system.
The method of claim 1, wherein in step four, the pulse dose ratio is adjusted from 0.7:1 to 3:1.
A dual-energy radiation system based on the method for improving the material recognition capability of a dual-energy radiation system according to claim 1, comprising: a dual-energy radiation source, a radiation detector, a dual-energy image acquisition device, and a judgment processing module And adjusting a processing module, a control module, and a storage module; wherein

The dual energy radiation source emits a dual energy radiation beam to perform dual energy scanning;

The radiation detector receives the dual energy radiation beam, converts the dual energy radiation beam into a digital signal, and sends the signal to the dual energy image acquisition device;

The dual-energy image acquiring device generates a dual-energy radiation image according to the received digital signal;

The judging processing module judges whether the detected data is consistent with the test sample according to the scan detection result included in the dual-energy radiation image, and if the judgment result is inconsistent, the judgment processing module sends the judgment result to the adjustment processing module; if the judgment result is consistent, the judgment processing The module sends the judgment result to the storage module;

The adjustment processing module adjusts the pulse number ratio or the pulse dose ratio of the dual energy radiation source, And transmitting the adjustment result to the control module;

The control module controls the dual-energy radiation source, so that the dual-energy radiation source emits a dual-energy radiation beam according to the adjustment result of the adjustment processing module;

The storage module stores the pulse number ratio or the pulse dose ratio of the current dual-energy radiation source as the scan job ratio corresponding to the test sample according to the judgment result of the judgment processing module.
The dual energy radiation system of claim 3 wherein said adjustment processing module adjusts the pulse dose ratio from 0.7:1 to 3:1.
A method for improving material recognition capability of a dual energy radiation system, comprising:

Step 1: Determine the type and thickness of the test sample;

Step 2: performing dual-energy scanning detection on the test sample having the first type and the first thickness, and obtaining a scanning detection result;

Step 3: According to the scan detection result, it is judged whether the system criterion reaches a minimum value. If the minimum value is not reached, step 4 is performed; if the minimum value is reached, step 5 is performed;

Step 4: Adjust the pulse quantity ratio or pulse dose ratio of the dual energy radiation system, and return to step 2;

Step 5: determining the current pulse ratio or pulse dose ratio as the scan operation ratio of the dual energy radiation system;

The system criterion is
or
The lower corners 1exp and 2exp respectively represent the scanning detection results corresponding to the high energy pulse radiation and the low energy pulse radiation, ΔT is the measurement deviation for the radiation pulse dose, t is the thickness of the material, and Z i represents the equivalent atomic number of the i-th material. n is a positive integer in which the equivalent atomic number of the material corresponds to the type of material.
The method of claim 5, wherein in step four, the pulse dose ratio is adjusted from 0.7:1 to 3:1.
A dual-energy radiation system based on the method for improving the material recognition capability of a dual-energy radiation system according to claim 5, comprising: a dual-energy radiation source, a radiation detector, a dual-energy image acquisition device, and a judgment processing module , adjustment processing module, control module and storage module Block; among them,

The dual energy radiation source emits a dual energy radiation beam to perform dual energy scanning;

The radiation detector receives the dual energy radiation beam, converts the dual energy radiation beam into a digital signal, and sends the signal to the dual energy image acquisition device;

The dual-energy image acquiring device generates a dual-energy radiation image according to the received digital signal;

The judgment processing module determines whether the system criterion reaches a minimum value according to the scan detection result included in the dual-energy radiation image, and if the minimum value is not reached, the judgment processing module sends the judgment result to the adjustment processing module; if the minimum value is reached The judgment processing module sends the judgment result to the storage module;

The adjustment processing module adjusts the pulse quantity ratio or the pulse dose ratio of the dual energy radiation source, and sends the adjustment result to the control module;

The control module controls the dual-energy radiation source, so that the dual-energy radiation source emits a dual-energy radiation beam according to the adjustment result of the adjustment processing module;

The storage module stores the pulse number ratio or the pulse dose ratio of the current dual-energy radiation source as the scan job ratio corresponding to the test sample according to the judgment result of the judgment processing module.
The dual energy radiation system of claim 7 wherein said adjustment processing module adjusts the pulse dose ratio from 0.7:1 to 3:1.